2008 年 33 巻 1 号 p. 61-64
Pb(Zr,Ti)O3 (PZT) thin film capacitors have been widely investigated, due to their various applications, including ferroelectric memories and micro-electromechanical systems. However, degradation of electrical properties of the films is caused by crystal defects, and the exact mechanism for this has not been fully elucidated. We have attempted to investigate defects in the films by thermally stimulated current (TSC) measurements, and the identification of the observed TSC peaks and the relationships between the degradation and TSC signal. However, the behavior of carriers in the films, such as recombination, has not been fully elucidated, and quantitative evaluation of carrier movement and defect density has been difficult. We have therefore investigated the influence of UV-light irradiation on electrical properties of PZT film capacitors. The leakage current and capacitance measurements under UV light (= 250 nm) irradiation were carried out. The current and capacitance were gradually changed by the irradiation, revealing that the relaxation time and lifetime of carriers in the films were sufficiently high, above 100 s, and the decrease in the observed current in TSC by recombination seems to be small. The relaxation time slightly decreased with increasing temperature and applied voltage because of carrier drift. The drift properties were also discussed.
